Other SystemsThis page describes other positioning systems that have been used by the oceanographic and DP industries up till now. If you know of a system I have omitted please send me the details and I will add it to the list.Alpha Also known as RSDN-20, Alpha is a Russian long range Radio Navigation System, which operates in the Very Low Frequency (VLF) band. It is thought to date from the 1950's and there are five known transmitters, located at Novosibirsk (master station), Krasnodar, Khabarovsk, Revda and Seyda. The transmission format is six time slots each 400mS wide and followed by a 200mS gap, making a total cycle duration of 3.6 seconds. Each site radiates a CW carrier in its appointed time slot, on one of the frequencies 11.905 kHz, 12.045, 12.091, 12.649 kHz and 14.881 kHz. Determination of position is by comparing the phase at some common base frequency, however it is obscure how this is derived. The system is still operational at the time of writing and can easily be heard late at night using a VLF receiver of the 'whistler receiver' type with a short whip antenna feeding a very high impedance amplifier. More in depth information about Alpha may be found here, and details of VLF receivers of the type mentioned above here Argo Argo was a product of the Cubic Corporation of the USA. It was also known as DM54. It was a positioning system using phase comparison techniques and operating in the 1.6-2.0 MHz band. It offered accuracies of around 4 to 7 metres and had a maximum range of 400km. The way in which Argo operates is significantly different to that of Hi-Fix or similar systems; it operates primarily in the range-range mode with up to seven mobile stations being able to use the same shore stations by means of time sharing. There is also a hyperbolic mode that allows an unlimited number of users to share the system. An Argo chain consists of a master station and four slave stations. The transmission cycle is two seconds long, and is divided into seven 'sub-cycles', each of which is further divided into 44mS time slots in which a station may radiate a 36mS long RF pulse- except for the first time slot in a sub-cycle, in which the master station transmits a triggering pulse which is 120mS long. The cycle commences when the master station radiates a trigger pulse that, because of its length, is uniquely identifiable by all stations. On receipt of the trigger pulse, the first ship-borne (mobile) station will transmit an interrogation pulse in the next time slot. This pulse is received by all of the slave stations, which measure the phase difference between the interrogation pulse and their own synthesised master oscillator. Each of the slaves then replies in turn in one of the four following time slots, with an RF pulse whose phase is adjusted to replicate that of the received phase. The mobile receiver receives all of these replies, and computes its postion by comparing the round-trip phase delay to each slave station. Following the next trigger pulse, the next mobile will transmit and so on until all seven will have obtained positions. There then follows a period of silence before the cycle repeats. Lane identification can be used and requires the use of a second radio frequency approximately 10% higher than the main. The mobile operator can initiate a lane-check, transmissions are then made alternately on the lane identification frequency until the control unit has computed the lane error, which is presented to the operator as a number of lanes. Argo stations comprise a Range Processing Unit (RPU) and an antenna coupling unit. The arangement is the same for all stations, except that the mobile requires an additional control and display unit. The transmitter output is up to 100 watts. The units are pre-programmed with up to 16 frequency pairs, and no retuning is required over a 200kHz switching bandwidth. The transmitter incorporates SWR monitoring and will reduce the output power to safe levels when working into a poorly matched load. Antennas can be between 8 and 30 metres high. A feature of the system is the ability to integrate with a variety of other systems due to a number of flexible interfaces; GPIB and RS232 both being provided. Artemis Artemis was a short range positioning system developed by CHL of the Netherlands. Operating at microwave frequencies, the system offered exceptional accuracy (0.5m) at short ranges; normally about 1.5km but which could be extended to 25km with the high-power transmitter option. It was typically used with the fixed stations installed on oil rigs, and used to provide positioning to diving tenders and other vessels working in the area. No further information available. BRAS/RS-10 (БРАС/РС-10) BRAS and RS-10 are similar hyperbolic position fixing systems which continue to be used in the countries of the former Soviet Union. Their transmissions, thought to originate from chains located around the Baltic coast, may be heard on frequencies around 1810 kHz. The BRAS system appears to comprise a master and two slave stations that transmit sequentially, with a cycle time of about 0.9 seconds. Unusually, instead of a continuous-wave (CW) transmission the chain stations are modulated by a series of pulses at 820 Hz repetition rate, so that the transmission sounds like a series of carriers 820Hz apart when tuned on a conventional receiver. RS-10 uses the same transmission format but allows for a master and up to five slave stations. Read my BRAS/RS-10 page by clicking here. Chayka (ЧАЙКА) Chayka is the name of a Russian Radio Navigation System (RNS) that is extremely similar to Loran-C, and you should see Loran sites for more information. There is a high degree of compatibility between the systems and the Chayka chains in the North of Russia are usable by Loran-C receivers. The system has been integrated into the Eurofix (QV) system. Click this link, select the Chayka/Loran-C link, and be prepared to be amazed!! Consol Consol was a beacon system operating at around 300kHz that used an array of 3 phased antennas to produce a rotating pattern of dashes and dots. Following the callsign sent in CW, the listener heard a sequence of dashes that gradually merged into a continuous tones, followed by emerging dots. The whole sequence lasted abot 40 seconds. The British Consol system, and its very close German counterpart code named ,Elektra Sonne' were used extensively for marine navigation during WWII. There is an excellent description and historical perspective at Jerry Proc's web site, here. Be sure to check out the pics of the derelict Lugo station here. I have prepared an audio simulation of the last remaining Consol station LEC at Stavanger, Norway which continued in operation until around 1990. The method of use was to count the dashes to the equisignal zone, then count the dots. A methematical formula gave the bearing off the station. The theoretical accuracy was 0.6 degrees of arc, or 3 miles at 1000 miles. Datatrak Datatrak is a medium-area LF automatic vehicle location (AVL) system operating in the UK, Benelux countries, Germany and Austria. It is operated by Securicor Information Systems in the UK and by Siemens-Datatrak in mainland Europe. It was originally developed to fulfil a need for the monitoring of Securicor's own parcel and security vehicles, however it is now marketed to a number of other customers. The system is a conventional hyperbolic positioning system where a number of stations making up a chain transmit in sequence on a common pair of frequencies in the band 130 to 170 kHz. The receiver calculates it's position and communicates this back to the control centre (Swindon in the UK) by means of a UHF radio system that provides similar coverage to the LF network. The system is enhanced by the provision of Event Activated Tracking (EAT) or 'Trak Bak' as Securicor call the product. This allows a stolen vehicle to be tracked and aprehended. Also, the UHF component may monitor various inputs from the vehicle, providing a telemetry function. There are apparently 14 sites in the UK but their location is unknown. The sequential transmissions are clearly audible at around 145 kHz in the UK, the interesting thing about them is that they 'warble' as if FSK modulated at around 20bps. Using Manchester coding, the transmission would still be usable for positioning as long as the phase were averaged over many symbols. Decca The Decca Navigator System was the most developed, most accurate, and undoubtedly the most commercially successful of the Low Frequency (LF) radio navigation systems. There are few applications that Decca did not fit, starting life in 1937 it was initially used as a maritime navigation aid, guiding the D-Day invasion forces in 1944. However in the 1950's and 60's when the jet airliner began to open up the air routes of the world, many were fitted with Decca receivers. The system operates using, within each chain, a master and a number of slaves- designated red, purple and green. Each transmitter radiated a continuous carrier at a frequency which was a multiple of the base frequency; different chains avoided interference by using different frequencies but all were in the band 70 to 130kHz. In the receiver, the phase of the received signals were compared with each other at the base frequency, and indicated on special phase meter dials called Deccometers. The user transferred the readings onto a map overprinted with a special hyperbolic lattice to obtain a fix. The Decca chains in the UK ceased to operate at midnight on 31st March 2000, marking the end of nearly 60 years of service.
DeltaFix was a modification of Racal's Hyperfix positioning system, so that Differential GPS (DGPS) data could be transmitted using the Data time slot in the Hyperfix transmission sequence. See my DeltaFix page. Electronic Position Indicator (EPI) EPI was developed by the Coast and Geodetic Survey of the US (later to become NOAA) under Clarence Burmister. It was designed to have the best features of both LORAN and SHORAN, and had a typical range of 250 miles. Development started in 1944 and it was first used in 1947 in the gulf of Mexico. It was used on some significant surveys such as in the Bering Sea, and the US West Coast, and remained in use until 1955. A web page shows an EPI shore station mast, and from this it appears that it probably worked at MF frequencies. No further information available. Eurofix Eurofix is not a navigation system in its own right. Rather, it is a method whereby Differential GPS (DGPS) corrections are transmitted using existing Loran-C transmitters. See this link for more details. If it is successul in the market, it will extend the life of the North European Loran chains indefinitely. GEE GEE was a radio navigation system operating in the VHF band. It was developed during WW2 by a team working under R.J. Dippy at the Telecommunications Research Establishment of the British Government. It was put into service as the primary means of navigation over enemy territory by the RAF, and receivers were carried on most bombers. The system operated in hyperbolic mode, the ground transmitters radiating narrow pulses and the receiver measuring the difference in time-of-flight. The receiver presented received pulses on a CRT display, and the user measured the times by aligning 'strobe' pulses with the received pulses on the display and reading off numbers which were transferred to a map overprinted with a hyperbolic lattice. The system remained in use until 1970. More information can be found here. Hydrotrac Hydrotrac is a positioning system developed and manufactured by Odom Offshore Surveys Inc. of the USA. It operated in the MF band over a frequency range of 1.6 to 2 MHz. It was capable of providing an accuracy of down to 2 metres with a maximum range of 250 nautical miles during the day and somewhat less than half this at night. Hydrotrac has some features in common with Hi-Fix, such as the use of sequential transmission on the same frequency from a master and up to three slaves, and a triggering signal 60Hz below the pattern frequency. The transmission cycle period is 1.0 seconds with two slaves, and 1.3 seconds with three. The system could be operated in either hyperbolic or range-range mode. Master station (and ship station if used in range-range mode) consisted of a master drive unit (MDU), power amplifier (PA) and an antenna coupler unit, while the slave station equipment consisted of a slave drive unit (SDU), power amplifier (PA), and antenna coupler unit. The RF frequencies were generated by a frequency synthesiser which could be set to any 10Hz step in the band 1600-2000 kHz, and the RF power output of the transmitter PA unit was continuously variable up to 150 watts. The antenna coupler unit permitted antennas of from 10m to 45 m height to be tuned, and the PA contained integral SWR metering. The nominal power supply was 24 volts, negative ground. One significant difference from Hi-Fix was the way in which station timing was derived. In order to eliminate lane loss through loss of synchronisation, the units contained a timing system that was essentially accurate without external triggering; such that timing would remain in synchronisation over a period of several hours. The receiver was designed so that 256 consecutive valid triggers had to be received before the timing system was updated. Loran-C Loran-C is a wide-area radio navigation system that covers large parts of the world. The system was built by the US government but subsequently handed over to the countries in which the transmitters are located. It operates at 100kHz in the low frequency band, using pulse transmissions. It is documented thoroughly elsewhere: click here for a Google search. Loran-C is currently still operating although closure is imminent, however the introduction in Europe of Eurofix may extend its life. The Loran-C chains around the UK are part of the North Europeans Loran-C System (NELS); this organisation did have a very informative web site but the lease on the domain expired on 18th May 2006 and so far has not been renewed. Link... I will shortly post an audio file but in the meantime, here's a simulation which is incredibly accurate. It's of the transmission from a slave station with a GRI of 7000. MARS-75 (MAPC-75) A system still in use in Russia. Very little is currently known about this system. Microfix Microfix is a Racal product. It operates at C-Band microwave frequencies (5 GHz) in a similar way to the Motorola Miniranger described below. The stated accuracy of the system is 1 metre and the maximum range is 80km over a line-of-sight path. There is a mast-head unit containing the transmitter-receiver electronics and antenna, and a control-display unit (model 90600) somewhat similar in appearance to the 90515 Hyperfix receiver. Link to Hydroquip Ltd with more information and picture. Miniranger Miniranger is a product of the Motorola Corporation. It went through many development stages as Miniranger I/II/III; it is also known as 'Falcon' or 'Falcon IV'. It operates in the C-Band microwave region at around 5.5 GHz, although an X-band (9.5 GHz) otion is available. The transmitter power is 400 watts. The system works by measuring the 'time of flight' of short (0.3 uS) pulses of radio energy. A fix is obtained by comparing the distance measurement (range) obtained in this way from 2 or more shore stations. Whilst the accuracy obtained is good, as with all microwave systems the disadvantage is that at these frequencies, the radio range obtainable is strictly line of sight. The range may be extended by mounting the shore stations on high ground and/or tall structures, and the ship-borne antenna at the top of the mast. The accuracy of the system is better than 3 metres and the maximum range 37 km. Omega Omega, which ceased operation in 1997, was a wide area radio navigation system that operated in the Very Low Frequency (VLF) band. It provided near-global coverage from 8 transmitter sites located in Norway, Trinidad, Hawaii, USA, Reunion Island, Argentina, Australia, and Japan. The transmitters radiated a pattern of CW emissions in pairs on one of three frequencies, 10.2, 11.33 and 13.6 kHz. For more information see this link. Pulse-8 Pulse-8 was a Decca product, probably in use during the 1960's/70's. It is believed to have operated in the low frequency band, and radiated a pulse transmission very similar to Loran-C. If this is correct, then it was most likely to have been a hyperbolic system using both time-of-flight and phase comparison techniques, with station identification by means of pulse pattern recognition. No further information available. Radio Acoustic Ranging In the early years of the twentieth century, it had been discovered that sound waves propagated for large distances under water, and could be detected by a hydrophone (underwater microphone). This led to underwater bells being placed on wrecks or dangerous shoals to mark them, and the sound of the bell, which was audible for a range or 10 to 15 miles, would warn shipping. By the outbreak of WW1 networks of hundreds of bells existed. The development of directional hydrophones enabled bearings to be taken on the bells, and experiments into positioning by this means were carried out. The RAR system, developed in 1923, marked the first time that radio was applied to positioning, and it was the first positioning system to be usable in conditions of zero visibility or at night. It required two or more additional vessels, each fitted with a hydrophone and a radio transmitter, to be located in known positions. The survey vessel had a radio receiver. To obtain a fix, the survey vessel detonated an explosive charge underwater. The acoustic waves from the explosion travelled outwards away from the vessel, at a known velocity. When they were detected by the hydrophone on board one of the vessels, a radio signal was transmitted back to the survey vessel. In this way, a position was obtained by measuring the time delay between the explosion and the receipt of the radio signals. This gave a 'range off' of each vessel. Raydist The Raydist NR-S short range positioning system is a product of the Teledyne-Hastings corporation and was introduced in 1954. Operating in the MF and HF bands betwen 1.6 and 4.0 MHz, it can operate in either hyperbolic or range-range modes and has a maximum range of 250 miles by day and 150 miles at night. It has an accuracy of 10 feet in range-range mode. The equipment is portable and transistorised and operates from a 24V DC supply. The mobile unit ('Navigator') contains the reference oscillator for the system. The signal is relayed through the slave stations in the chain, and a positional fix is obtained by phase comparison. Seafix Seafix was a Decca product that was a version of Hi-Fix with few (if any) apparent differences. There is a document at the National Oceanographic Society of America's web site that contains a reference to Seafix and a some pictures of a ship installation and a shore based chain transmitter here. It also describes some of the other systems mentioned in this page. Or, you can just read all about it on my own SeaFix page. SHORAN SHORAN is a shortening of SHort RAnge Navigation system, after the style of LORAN- but the technical differences were many. SHORAN used frequencies in the VHF spectrum and had many similarities to Gee, a wartime development to help bombers navigate over enemy territory. Unlike Gee, which was a hyperbolic system, it was a range-range system using a transmitter on board the vessel to interrogate two shore stations. The round-trip time of the radio pulses was measured and this gave the distance off. SHORAN was first used in a hydrographical survey in 1945. Syledis Syledis (SYstem LEgere pour mesure le DIStance) was a positioning system manufactured by Sercel of France. It operated in the range 420-450 MHZ in the UHF band. During the 1980's the North Sea was covered by extensive Sysledis chains. The system offered good acccuracy at distances of up to 80km from the shore stations. Syledis remained active and well utilised until the early 1990's. It was used to validate the accuracy of GPS and DGPS based systems in their early days. It is believed to have operated using 'time-of-flight' range measurement. A Syledis beacon is installed at Flamborough lighthouse; the antenna is a four-stack dipole attached to the balcony. The system had a reputation for causing interference to radio amateurs using the 430 MHz band. No further information available. Trisponder Trisponder is a short-range position fixing system manufactured by Del Norte Technology Inc of the USA. It operates at X-band microwave frequencies around 9.5 GHz. By the use of relatively high power transmitters (1000 watts) it gives a range of up to 80 km and can obtain an accuracy of 3 metres under good conditions. The system comprises a number of shore-based transponder units and a vessel-mounted interrogator unit which interfaces to one or more dsiplay units. All units operate from a 24 V DC power supply and despite the high RF ouput power, the transmitter-receiver units consume only 17 watts of power. The principle of operation is that of time-of-flight range measurement, but by means of a time-sharing principle up to 4 mobiles can use the same shore stations. Last updates 23/9/06, 31/5/05 Return to index |